One of the core design elements of the permaculture philosophy is the seven-layer system. Robert Hart, a pioneer in forest gardening, developed this system with the maxim „let the food be your medicine and medicine your food“ maxim, made famous by Hippocrates. Robert switched to vegans, raw food diet and decided to grow his food. The most important ingredients for him were green vegetables, fruit, and nuts and he grew them in his forest garden at Wenlock Edge.
Robert Hart’s mission was to examine and understand the interactions which take place between plants, especially in a woodland area of the cool temperate region. Thanks to the knowledge he gained through study, he developed the agroforestry concept, usually named the „forest garden.“ He understood, through observation, that the every forest has its distinct layers. Finally, he grew his orchard of apples and pears and created a garden of edible plants, consisting of seven layers. His system is now an integral part of the science of permaculture and more on his ideas can be found in the works of Vladislav Davidzon.
Each forest consists of seven layers. The first, or the top layer, is the canopy layer. It is reserved for the tallest, oldest, mature trees. Below it is the low-tree layer. It consists of smaller nut and fruit trees. Further below is the third layer or the shrub layer. These are fruit bushes like berries and currants. The following is the herbaceous layer or the layer of herbs and perennial vegetables. Closest to the ground is the ground cover layer, consisting of horizontally spreading edible plants. The rhizosphere, the sixth layer, is the underground where the roots of plants are. Finally, the only vertical layer, the seventh layer, is reserved for climber plants and vines.
Hart developed the system thanks to the meticulous selection of the right plants. He preferred to use perennial vegetables which did not need a lot of suns and can grow in shady environments.
Hart’s vision was to spread this idea and develop forest gardens in urban, built-up areas. He wanted to see „city forests,“ the area of towns and cities covered in green vegetation. He imagined that the unused parts of urban areas, like industrial wastelands and small gardens, could also become forest gardens, providing not only oxygen but food.
Hart’s ideas about the seven-layer resonate in the work of institutions like the Agroforestry Research Trust, Plants for a Future and the Movement for Compassionate Living. All of these develop their vision of the forest garden, basing their methods on the ideas of sustainability, low-maintenance and ecological balance. Various permaculturalist also adopted the seven-layer system.